MONK,
Is there a method to achieve maximum optical properties of the crystals when precipitating the iron oxide?
When I worked with the nitrate of iron I played with a wash of baking soda after staining and then heating.
The baking soda wash causes foaming on the surface which lifts off some of the iron oxide created by the reaction between the baking soda (a caustic) and the ferric nitrate (a weak acid) on the wood. That gives very tiny crystals.
Doing the conversion from ferric nitrate to ferric oxide by just applying heat gives larger crystals but not a muddy look.
This thing about "chatoyancy" also relates to the structure of the wood. When you look at well scraped oak and then well scraped maple under a microscope you see a difference in the structure of the wood and the way each reflects light. Some woods like maple or alder takes on what might be called a "sheen" in the way it reflects light. Oak has a very coarse structure and does not reflect light as well.
In trying to understand why different woods looked different when stained I used a high-power microscope to look into the micro-structure of the wood. Some very large differences were seen.
Under the microscope the structure of the wood looks like a bunch of soda straws glued together. There are big differences in the structure of the tubes. The tubes in oak have double thickness double layer walls. Those in maple are thin walled and single layer.
E. Ogre
